Is there an effective way to train concentration and willpower?

Trainings by trainings ... but I still think that it is better to approach the problem in a complex way. In addition to puzzles, poems and mosaics, I also take multivitamins, fish oil and Evalar's theanine ... all together, I want to say, works great. I became more attentive, the brain seemed to be working to its fullest ... and this is very pleasing)

William James, one of the founders of modern psychology, advised to regularly shift matches to train willpower, for example, from one box to another and back. It was critically important that an exercise for willpower training did not make sense (except, in fact, it turns out, willpower training).

Regular exercise in complete garbage with the only goal and the result at the end - willpower.